Electron lithographic or detection systems typically use a single electron beam to expose or image a substrate. A single beam approach, however, poses severe limitations to the maximum achievable pixel rate, whether used for pixel exposure or pixel detection. In order to satisfy the throughput requirements of present day manufacturing environments several techniques are being developed to increase this pixel rate. For example, one technique used to increase throughput is to increase the number of electron beams that are used for exposure or detection.
In order for such a multiple electron beam system to function properly numerous requirements must be met for each single beam, i.e., each beamlet, as well as the collection of beamlets, i.e., the array. Crucial parameters for each beamlet include, e.g., spot size, brightness, beam uniformity and energy spread, while parameters for the array include uniformity, reliability and manufacturability standards.
In a multi-beam system it is typically desirable to have the ability to individually extinguish each beamlet independently, i.e., blanking a beam. Conventionally, a beam is blanked by shifting the direction of the beam away from a transmission aperture thereby stopping the flow of electrons through the aperture. Electron beamlets, however, propagate in close proximity to each other and, thus, such an approach might be undesirable. The stray electrons created by this type of blanking action could very well disturb the propagation of the neighboring beamlets. It is therefore preferred to extinguish the beamlets at the source thereby preventing any unneeded electrons from entering the optical system.